A variety of devices for making dental impressions of a patient's teeth are known. The term "dental impression" is used in the dental trade to designate a specific functional object and is distinguishable from the more general term "impression". Specifically, a dental impression provides a mold which is, in essence, an exact replica of the reverse image of a dental arch or arches or area of a dental arch. A dental impression is classified as full arch upper maxillary, full arch lower mandibular, anterior, quadrant, or bite registration. Dental impression focuses on the precise size and position of the teeth, the gingival tissues, and any surgical alterations so that a working model may be produced. It is on this working model that a dental prosthetic device will be fabricated for eventual insertion into the mouth of a dental patient.
The material used for making dental impressions must satisfy specific requirements established by the American Dental Association (ADA), Council on Dental Materials (Revised Specification No. 19 for Non-Aqueous, Elastomeric Dental Impression Materials). A copy of Revised Specification 19 is enclosed with this application and is incorporated herein by reference. Specifically, the ADA requires that elastomeric dental impression materials have a certain dimensional integrity, elastomeric distortion limit, recovery rate, detail capturing capabilities, as well as other physical parameters. Specifically, non-aqueous elastomeric dental impression materials are classified according to their elastic properties and dimensional change after "setting". Each type is further classified according to its apparent viscosity and intended use. Likewise, the aforementioned working model must fulfill specific requirements related to accuracy and hardness.
A number of dental impression devices, processes and/or the compositions are known. While these known dental devices, processes, and compositions provide a means for dental impressioning, there are certain disadvantages associated with their use. One such disadvantage is that these known processes generally require the use of a dental impression tray. These impression trays are made of various stock or custom made sizes to accommodate the specific type of dental impression desired. Furthermore, some of these dental impression processes involve a pre-step prior to the actual impression step. In addition, although several of the known dental impressioning processes allow for two or more types of dental impressions to be taken at the same time, such methods generally require the use of an impression tray and/or a time-consuming pre-step prior to the actual impression step.
Presently, the predominant use is with three elastomeric dental impression materials used with impression trays and in other related dental impression procedures. These three materials are polysulfides, silicones, and polyethers. Each of these materials involves the previously mentioned pre-step or two-part chemical reaction cure system that is costly, time-consuming to implement, and subject to shelf-life age changes. Furthermore, each of these materials are messy to work with and require a clean-up phase following their use. Additionally, due to the nature of cure for each of these materials, they are said to be thermoset. In other words, once these materials have reacted, they are permanently changed and cannot be used again. This creates a great expense for the dentist who frequently does not obtain a suitable impression of the teeth or tissues to his/her satisfaction as a result of, for example, a gagging patient, and must redo the impression which involves using new material, a new impression tray, and an additional mess.
Generally, each of the dental impression materials are mixed to a pasty consistency and placed into an impression tray that acts as a carrier. The filled impression tray is placed and pressed into the patient's mouth. The procedure and the materials used generally create a time consuming clean-up.
Furthermore, present dental impression techniques which provide for multiple types of dental impressions at one time generally involve the use of an impression tray and a pre-step prior to the dental impression step. In addition, these same dental impression techniques are used to make master models from which functional dental devices are designed. For example, master models are presently used for fabricating tempro-mandibular joints, bruxism or night guards, anti-snore devices, denture relines, mouth guards, retainers or bite risers, and other similar functional dental devices. Such devices essentially differ from one another in the materials or material formulas used for their construction, their intended purpose, and the method of their construction.
Some of the patents which implement these materials and/or involve the use of impression trays are described in U.S. Pat. Nos.: 4,472,140; 4,867,680; 5,011,407; 5,059,120; 5,066,231. These patents show that dental impression trays are made of various stock or custom made sizes for accommodating the specific type of dental impression material desired. In addition to the foregoing, U.S. Pat. No. 3,312,218 discloses an impressionable mouth protector. Each of the aforementioned patents is described in greater detail below.
U.S. Pat. No. 5,066,231 discloses the use of a blend of high and low molecular weight polycaprolactone for use as a dental impression material. As a practical matter, the use of this material would be very limited to edentulous arches (no teeth) due to its inherent stiffness, inability to flex out from undercut areas, and inability to avoid entrapment in interproximal spaces.
U.S. Pat. Nos. 4,472,140 and 5,059,120 disclose dental impression tray devices with various waxes, zinc-oxide eugenol pastes, silicone, plastics, self cured and light cured resins that are used in conjunction with film, gauze, and strips which act as separation layers. The impression tray device in the '140 patent carries the wax impression material to the patient's mouth. In addition, the '140 patent describes a method of acquiring multiple types of dental impressions at one time. For example, impressions may be simultaneously taken of upper teeth, lower teeth, and the bite registration. A foraminous film serves as a thin separator inside a metal or plastic frame which serves as the carrier of the dental impression material.
U.S. Pat. No. 4,867,680 discloses a dental impression tray device which uses a polymerizable preferably light cure impression material that includes various acrylates.
U.S. Pat. No. 5,011,407 discloses making a custom dental impression tray that is fabricated from polycaprolactone. The patient bites into a softened pre-formed piece of the material to register position of the teeth in the tray for a closed bite impression. The tray assembly is molded around the affected areas of the mouth and allowed to harden. A wax spacer layer is removed and the tray is then filled with dental impression material in the space where the wax was, such as silicone, and reinserted into the patient's mouth for the impression procedure.
U.S. Pat. No. 3,312,218 discloses a mouth protector which is made from a vinyl resin comprising an ethylene vinyl acetate copolymer, such as Elvax 250. Elvax 250 is typically used in paraffin wax systems where viscosity limitations are less stringent or where higher viscosities are required.
Thus, while the aforementioned patents disclose a variety of devices and methods for dental impressioning, there are still some problems associated with their use.
Accordingly, an object of the present invention is to provide a method and composition for dental impressioning that is convenient and easy to use.
Other objects and advantages of the invention will appear hereinafter.